The interosseous intermetatarsal ligaments are short, strong bands connecting the bases of adjacent metatarsals, running transversely between the medial and lateral surfaces of the second through fifth metatarsal bases. They are deep to the plantar and dorsal ligaments at the metatarsal bases and maintain the transverse integrity of the proximal forefoot. In Lisfranc anatomy, the interosseous ligament between the medial cuneiform and the second metatarsal base (Lisfranc ligament proper) is the most important.
Resist lateral and dorsal displacement of the metatarsal bases relative to each other, maintain the proximal forefoot arch width, and contribute to the overall rigidity of the Lisfranc joint complex.
The interosseous intermetatarsal ligaments are disrupted in Lisfranc injuries, where diastasis between the first and second metatarsal bases on weight-bearing radiograph (greater than 2 mm) indicates ligament failure. The Lisfranc ligament proper (cuneiform-metatarsal 2) must fail for complete Lisfranc instability to occur. Smaller interosseous ligament tears between adjacent metatarsal bases produce subtle Lisfranc sprains that may be missed on non-weight-bearing X-rays, requiring weight-bearing comparison films or MRI for diagnosis.
Partial tears of the interosseous intermetatarsal and Lisfranc ligaments without frank diastasis produce midfoot pain and tenderness at the Lisfranc joint line that may be missed on routine films; weight-bearing AP films demonstrating any widening greater than 2 mm between the first and second metatarsal bases confirm instability requiring protected weight-bearing or surgical fixation.
